Multi-SIM (subscriber identification module) wireless devices have become increasing popular because of their flexibility in service options and other features.
In various types of multi-SIM wireless communication devices, each modem stack associated with a subscription may store information provisioned by its respective network operator in a SIM, which may allow the SIM to support use of various different communication services. For example, various wireless networks may be configured to handle different types of data, use different communication modes, implement different radio access technologies, etc. One type of multi-SIM wireless device, referred to as a dual-SIM dual-active (DSDA) device, is typically configured with separate transmit/receive chains associated with each SIM, thereby allowing simultaneous active connections with the networks corresponding to two SIMs. Some DSDA devices, referred to as single transmit DSDA devices, are configured with separate receive chains associated with each SIM, and a single shared transmit chain, which reduces hardware costs and power requirements of the device.
When a DSDA device is involved in simultaneous voice calls on both SIMs, one call will be active, and the other call is placed on hold. On the held call, as well as during periods of silence on the active call, voice packets are not transmitted, but control messages and silence descriptor (SID) frames are transmitted at regular intervals over the air interface. Therefore, transmission conflicts may arise when time slots for transmission align between the SIMs. For example, on a single transmit DSDA device, a scheduling conflict may arise when use of the transmit chain is required by both SIMs during aligned time slots. Further, in a DSDA device configured with separate transmit circuitry for each SIM, collisions may arise when the SIMs simultaneously transmit on their respective communication links due to coexistence issues (e.g., radio frequency (RF) interference). As a result, one or multiple transmissions maybe dropped or delayed, increasing power consumption and/or degrade performance.